1. Field of the Invention
The present invention relates to a particle (grain) size measuring apparatus, which detects a diffraction/scattered light or dynamic light scattering by irradiating a laser beam onto a particle group such as a dispersing powder sample or the like, and measures a particle size distribution of the particle group on the basis of a scattered light intensity signal or the like obtained by the detection and more particularly provides an automatic validation and instruction mode.
2. Description of the Prior Art
Conventionally, a particle size distribution measuring apparatus using a light diffraction phenomenon or scattering phenomenon by a particle has calculated a particle size distribution of a sample particle in the following manner. More specifically, the above apparatus measures intensity distribution of a diffraction light or a scattered light, that is, a relation between a diffraction angle or scattering angle and a light intensity, and then, carries out arithmetic processing based on a Frauunhofer diffraction theory or Mie scattering theory with respect to the measured result. In the above manner, the above apparatus has calculated the particle size distribution of a sample particle. The above particle size distribution measuring apparatus has been used for research and development of raw materials in most mining and industrial fields such as the cement or the ceramic industry, and in a new material field mainly using ceramics.
For example, to give an example of the above apparatus, there is a particle size distribution measuring apparatus disclosed in Japanese Examined Patent publication No. 6-43950. FIG. 16 is a view schematically showing a construction of the particle size distribution measuring apparatus disclosed in this Publication. In FIG. 16, a reference numeral 10 denotes a cell comprising a transparent container for receiving a sample solution 11 dispersing a particle group of the measuring object in a proper dispersion medium, and a reference numeral 12 denotes a laser beam source provided on one side (backward side) of the cell 10. A parallel laser beam 13 emitted from the laser beam source 12 is enlarged by a beam expander (not shown), and then, is irradiated to the cell 10 in an enlarged state.
In FIG. 16, a reference numeral 14 denotes a condenser lens provided on the other side (forward side) of the cell 10, and a ring detector 15 is arranged at a focal position of the condenser lens 14. The ring detector 15 is constructed in a manner that a plurality of photo sensors having mutually different radii and a ring or semi-ring light receiving plane is arrayed concentrically around an optical axis of the condenser lens 14. Further, the ring detector 15 receives light scattered/diffracted at a relatively small angle to the optical axis of the laser beam 13 diffracted or scattered by particles in the cell 10 for each scattering angle, and then, measures their light intensity.
Moreover, a wide angle scattered light photo detector group 16 is provided at the vicinity of the cell 10. The wide angle scattered light photo detector group 16 individually detects light scattered/diffracted at a relatively large angle to the optical axis of the laser beam 13 diffracted/scattered by the particles in the cell 10 for each scattered light. Further, the wide angle scattered light photo detector group 16 is composed of a plurality of photo sensors 17 to 22 provided at an angle different from the condenser lens 14 and the ring detector 15. Thus, the photo detector group 16 can detect a wide angle scattered light exceeding a predetermined angle by the particles in the cell 10 in accordance with each oriented angle. In the photo detector group 16, the photo sensors 17 to 20 detect a forward scattering light, the photo sensor 21 detects a side scattering light, and the photo sensor 22 detects a backscattering light.
A reference numeral 23 denotes a pre-amplifier for amplifying an output of the photo sensors constituting the ring detector 15, and a reference numeral 24 denotes a pre-amplifier for amplifying each output of the forward scattering light photo sensors 17 to 20. Further, a reference numeral 25 denotes a pre-amplifier for amplifying each output of the side scattering light photo sensor 21 and the backscattering light photo sensor 22. A reference numeral 26 denotes a multiplexer for successively capturing each output of the pre-amplifier groups 23 to 25 and transmitting it to an A-D converter 27, and a reference numeral 28 denotes a computer which is used as an arithmetic processor for inputting an output from the A-D converter 27. The computer 28 stores a program for processing each output converted into a digital signal (digital data relative to light intensity) of the ring detector 15 and the photo sensors 13 to 22 on the basis of a Frauunhofer diffraction theory or Mie scattering theory, and obtaining a particle size distribution in a particle group.
In the above particle size distribution measuring apparatus, in a state that the sample solution 11 is received in the cell 10, when the laser beam 13 is irradiated from the laser beam source 12 to the sample cell 10, the laser beam 13 is diffracted or scattered by the particles in the cell 10. Of the diffracted light or scattered light, a light having a relatively small scattering angle is imaged on the ring detector 15 by the condenser lens 14. In this case, the photo sensor arranged on the outer side receives a light having a larger scattering angle; on the other hand, the photo sensor arranged on the inner side receives a light having a smaller scattering angle. Therefore, a light intensity detected by an outer-side photo sensor means a quantity of particles having smaller particle diameter (particle size); on the other hand, a light intensity detected by the inner-side photo sensor means a quantity of sample particles having larger particle diameter. The light intensity detected by each of these photo sensors is converted into an analog electric signal, and further, is inputted to the multiplexer 26 via the pre-amplifier 23.
On the other hand, of the laser beam 13 diffracted light or scattered by the particles, a light, which is not converged by the condenser lens 14 and has a relatively large scattering angle, is detected by the photo sensors 17 to 22, and then, its light intensity is measured. In this case, the forward scattering light photo sensors 17 to 20, the side scattering light photo sensor 21 and the backscattering light photo sensor 22 successively detect a scattering light from a particle having a small particle size. The light intensity detected by each of these photo sensors 17 to 22 is converted into an analog electric signal, and further, is inputted to the multiplexer 26 via the pre-amplifier groups 24 and 25.
The multiplexer 26 captures measurement data from the ring detector 15 and the photo sensors 17 to 22, that is, an analog electrical signal in a predetermined order. The analog electric signal captured by the multiplexer 26 is made into a serial signal, then, is converted by the A-D converter 27 into a digital signal in succession, and thereafter, is inputted to the computer 28.
Subsequently, the computer 28 processes the light intensity data for each scattering angle obtained by each sensor of the ring detector 15 and the photo sensors 17 to 22 on the basis of a Frauunhofer diffraction theory or Mie a scattering theory.
As described above, in the above particle size distribution measuring apparatus, a light intensity distribution of scattering light having a substantially larger particle size is measured by the ring detector 15 and a light intensity distribution of wide-angle scattering light having a mainly smaller particle size is measured by the photo sensors 17 to 22. Further, the output of these ring detector 15 and photo sensors 17 to 22 is processed by the computer 28. Therefore, it is possible to obtain a particle size distribution of particle group over a wide range from a relatively larger particle size to a micro particle size.
By the way, the particle size distribution measuring apparatus as described above requires periodically carrying out a validation work in order to make a decision whether or not its measuring accuracy is correctly made. In particular, in a pharmaceutical company, in the case where the above particle size distribution measuring apparatus is used for a quality control, the validation work must be correctly done at least once per year.
In order to correctly do the validation of the particle size distribution measuring apparatus, an operator must measure a predetermined standard sample according to a determined procedure. For this reason, in the conventional particle size distribution measuring apparatus, the operator prepares a validation manual recording procedures of the above validation work, and then, must carry out the validation work according to the determined procedures.
However, a measuring technique using the above particle size distribution measuring apparatus is complicated, and therefore, it is difficult for an inexperienced operator to memorize and operate all of the working procedures. For this reason, in the case where an inexperienced operator operates the above apparatus, the operator must operate a control unit while referring to a user manual. In fact, when an inexperienced operator performs the above operation while referring to a user manual, such an operator can easily make a mistake in the sequence of work, and may not notice the mistake. Therefore, validation cam be incorrectly carried out; and for this reason, the resulting numerical value has no reliability.
In such a case, the measurement procedure must be performed again. However, in order to again make a measurement, the following steps are required. More specifically, dispersion medium and standard sample in a sample supply apparatus are discharged, and the sample supply apparatus is washed, and thereafter, the dispersion medium and standard sample are charged in the supply apparatus. Excessive time and labor are spent for doing the above work, and in the case where the standard sample is valuable, there is a possibility that many standard samples are wasted.
After the validation work is completed, the operator makes a report based on the measurement result, and must store the report; however, there is the case where the operator forgets this work. For this reason, there is a problem that no record is stored in spite of carrying out the validation work.
In addition, the above scattering type particle size distribution measuring apparatus uses precision optical components, a laser beam source, a motor and the like; for this reason, there is a possibility that an accident happens in the case where a user disassembles the apparatus in error, or makes a handling mistake. In order to prevent such an accident, conventionally, caution procedures have been prescribed in a manual or the like, or a label describing handling caution matters have been stuck onto the apparatus main body. However, the aforesaid accident happens due to a user""s careless mistake and an erroneous operation by an inexperienced operator; for this reason, there is a possibility that the number of processes may be required on a maker side or user side.
The present invention has been made in view of the aforesaid problems in the related art. It is, therefore, an object of the present invention to provide a particle size distribution measuring apparatus, which has a function of informing an operator of a procedure of validation work of the particle size distribution measuring apparatus, and thereby, can prevent a generation of mistake in a complicated validation work.
In order to achieve the above object, the present invention provides a particle size distribution measuring apparatus comprising: a storage medium which records a validation data indicating a procedure of validation work for a particle size distribution measuring apparatus, and a control unit which has a validation help function which successively reads a validation procedure from the validation data and successively carries out a control for the particle size distribution measuring apparatus according to a measuring procedure requiring no operation by an operator in the validation procedure while teaching the operator a work procedure requiring an operation by the operator.
Therefore, when carrying out the validation work, the operator can use the validation help function, and thereby, can operate the particle size distribution measuring apparatus according to the work procedure given from the control unit in a predetermined order without making a mistake. Moreover, the measuring procedure which is controlled by only a control unit is automatically carried out, by which the control unit controls the particle size distribution measuring apparatus according to an operation sequence previously stored as validation data.
The measuring procedure automatically carried out by the control unit includes a procedure for setting a setup value of a measuring object sample such as a refractive index of a standard sample used for the validation work. Therefore, the operator has no need of carrying out troublesome various setup operations for the validation work.
Accordingly, the operator can perform the complicated validation work without referring to a manual, and thereby, it is possible to reduce the responsibility of the operator to the minimum, and to successively carry out the work procedure made by the operator step by step without making a mistake. This serves to more accurately perform the validation work.
In the case where the control unit has a warning function of pointing out the operator""s mistake in the work procedure to the operator, and teaching a proper validation work according to a correct work procedure, when the operator makes an erroneous operation, a warning is given from the control unit. Therefore, the validation work is accurately performed, so that a measured result having a high reliability can be obtained.
The following matter is considered as a possible aforesaid mistake in the work procedure; more specifically, the operator charges a standard sample unsuitable for the measurement condition. For example, it is considered that concentration and temperature of the charged sample are outside a range of measurement condition predetermined as a standard sample. In this case, the concentration of the sample is previously measured by a light transmittance, and then, in the case where the measured result is different from the sample concentration condition, the control unit can give an instruction to adjust the concentration of the sample to the operator. Moreover, the control unit may have a warning function which confirms the measurement condition during measurement of particle size distribution, and gives an instruction to the operator to retry the measurement in the case where the measurement condition is beyond a range of a predetermined value.
In the case where the control unit has a speech (voice) output section for outputting an instruction to the operator by a speech signal, an operating instruction is given by machine generated speech; therefore, the operator can readily perform a validation work according to the spoken instruction without giving attention to reading a manual and the like.
In the case where the control unit has a monitor screen for displaying an instruction to the operator, the operator can obtain instructions for validation work via a display screen; therefore, it is possible to readily perform the validation work.
Moreover, in the case where the particle size distribution measuring apparatus of the present invention has an automatic charger for successively charging a standard sample used for the validation work into the above particle size distribution measuring apparatus, it is possible to reduce the work done by the operator to the minimum, and further, to easily handle the above apparatus. In this case, preferably, the control unit has a function of continuously measuring a plurality of standard samples.
The control unit has a judgment function of comparing an inspection result obtained from the validation work with a performance standard of the particle size distribution measuring apparatus, and making a judgment whether or not the comparative result is within the performance standard range. In this case, the operator has no need of collating the comparative result with a standard chart of the particle size distribution measuring apparatus, and making a judgment whether or not an error is within the performance standard range.
In the case where the control unit has a recording function of recording the inspection result obtained by the validation work, the inspection result is automatically stored after the validation work is performed. Even in the case where the operator forgets the output of the inspection result, it is possible to prepare a report using records of the inspection result automatically stored. Therefore, the record is not lost when carrying out the validation work. In this case, the record of the inspection result may be a result data stored in the storage medium, or may be an inspection result report outputted by a printer or the like.